One of Concrete’s Oldest Mysteries Has Been Solved

Even though concrete is the world’s most highly used construction material, scientists have failed to understand very important fundamental aspect of the material, until now.

A group of researchers from MIT, Georgetown, and CNRS in France believe they have finally figured out whether or not concrete is actually a solid, continuous material, like stone, or a group of materials that are packed so tightly together that they only act like a continuous material.  The team found that although there is always a smaller particle that fills open space in the concrete (which would make it a continuous material), concrete never really stops moving, which is why it’s susceptible to cracking and degrading.

So what’s the big deal about a bunch of science junkies looking at concrete through some microscopes and figuring this out? This research could lead to better, more environmentally stable concrete.  Because concrete is so widely used and it takes so much heat to cook limestone for cement mixtures, it is the world’s largest producer of greenhouse gases. Optimizing the cement mixture makeup to coincide with this new research data could not only reduce the amount of heat necessary, it could also lower the amount of water needed.

Speaking of water, it’s been widely accepted that the freeze-thaw cycle of water inside the concrete causes cracking as the water expands, but the team says that’s not actually the case.  Water can actually enter through pores which range in size from 15 to 20 nanometers (read: super small, one nanometer is one-billionth of a meter) and the water alone causes cracks and further concrete degradation without the help of freezing.

Full story: Riddle of cement’s structure is finally solved | MIT